U.S. patent number 7,888,623 [Application Number 12/378,173] was granted by the patent office on 2011-02-15 for illumination device and display device.
This patent grant is currently assigned to Sony Corporation. Invention is credited to Toshiyuki Kawashima, Takeshi Kodama, Shinji Ogawa.
United States Patent |
7,888,623 |
Kawashima , et al. |
February 15, 2011 |
Illumination device and display device
Abstract
An illumination device includes: a light emitting element to be
a light source; a light amount detecting means for detecting the
amount of light emitted by the light emitting element; a light
emitting element drive means for controlling drive current supplied
to the light emitting element so that the difference between the
light mount detected by the light amount detecting means and a
light amount target value becomes small; a junction temperature
detecting means for calculating junction temperature of the light
emitting element; and a setting means for setting the light amount
target value in accordance with the junction temperature detected
by the junction temperature detecting means.
Inventors: |
Kawashima; Toshiyuki (Saitama,
JP), Ogawa; Shinji (Tokyo, JP), Kodama;
Takeshi (Kanagawa, JP) |
Assignee: |
Sony Corporation
(JP)
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Family
ID: |
40954225 |
Appl.
No.: |
12/378,173 |
Filed: |
February 11, 2009 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090206236 A1 |
Aug 20, 2009 |
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Foreign Application Priority Data
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Feb 14, 2008 [JP] |
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2008-032743 |
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Current U.S.
Class: |
250/205; 315/152;
362/231 |
Current CPC
Class: |
H05B
45/28 (20200101); G01J 1/32 (20130101); H05B
45/22 (20200101); H04N 9/3182 (20130101); H04N
9/3194 (20130101) |
Current International
Class: |
G01J
1/32 (20060101); F21V 9/00 (20060101); H05B
37/02 (20060101) |
Field of
Search: |
;250/205,216,226,214C,214AL,552,553
;315/307,308,224,149,151,152,158,361,363
;362/227,234,85,108,230,231 ;257/79,82,88,89 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2004-184852 |
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Jul 2004 |
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JP |
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2004-226631 |
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Aug 2004 |
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JP |
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2007-027421 |
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Feb 2007 |
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JP |
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2007-087720 |
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Apr 2007 |
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JP |
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2007-087816 |
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Apr 2007 |
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JP |
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2007-165336 |
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Jun 2007 |
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JP |
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2007-537490 |
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Dec 2007 |
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JP |
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2008-509538 |
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Mar 2008 |
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JP |
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Primary Examiner: Epps; Georgia Y
Assistant Examiner: Williams; Don
Attorney, Agent or Firm: Lerner, David, Littenberg, Krumholz
& Mentlik, LLP
Claims
What is claimed is:
1. An illumination device comprising: a light emitting element to
be a light source; a light amount detecting means for detecting the
amount of light emitted by the light emitting element; a light
emitting element drive means for controlling drive current supplied
to the light emitting element so that the difference between the
light mount detected by the light amount detecting means and a
light amount target value becomes small; a junction temperature
detecting means for calculating junction temperature of the light
emitting element; and a setting means for setting the light amount
target value in accordance with the junction temperature detected
by the junction temperature detecting means, in which the light
emitting element has three color emitting elements including a
red-light emitting element generating light of a red wavelength
component, a green-light emitting element generating light of a
green wavelength component and a blue-light emitting element
generating light of a blue wavelength component, and in which the
setting means sets the light amount target value to be applied to
each color emitting element of the light emitting element by using
three temperature correction functions for each said color light
emitting element each pertaining to a function involving the
respective color emitting element and junction temperature
variation of one of the three color emitting elements such that for
a first color emitting element three respective temperature
correction functions are utilized which include a first temperature
correction function pertaining to a function involving the first
color emitting element and junction temperature variation of the
first color emitting element, a second temperature correction
function pertaining to a function involving the first color
emitting element and junction temperature variation of a second
color emitting element, and a third temperature correction function
pertaining to a function involving the first color emitting element
and junction temperature variation of a third color emitting
element.
2. The illumination device according to claim 1, wherein the light
amount target value is based on the difference between a first
junction temperature detected by the junction temperature detecting
means in a state that the light emitting element is driven in a
first drive condition and a second junction temperature detected by
the junction temperature detecting means in a state that the light
emitting element is driven in a second drive condition.
3. The illumination device according to claim 2, wherein the first
drive condition is the optimum drive condition of the light
emitting element which has been previously set.
4. The illumination device according to claim 1, wherein the
junction temperature detecting means includes a current reading
means for reading drive current supplied to the light emitting
element, a voltage reading means for reading drive voltage applied
to the light emitting element, a temperature measuring means for
measuring peripheral temperature of the light emitting element, a
storage means for storing thermal resistance between the light
emitting element and the temperature measuring means, and a
computing means for calculating junction temperature of the light
emitting element by using the drive current read by the current
reading means, the drive voltage read by the voltage reading means,
the peripheral temperature measured by the temperature measuring
means and the thermal resistance stored in the storage means.
5. A display device comprising: an illumination device irradiating
light; a light modulation means for modulating light irradiated by
the illumination device; and a projection means for projecting
light modulated by the light modulation means, and wherein the
illumination device includes a light emitting element to be a light
source, a light amount detecting means for detecting the amount of
light emitted by the light emitting element, a light emitting
element drive means for controlling drive current supplied to the
light emitting element so that the difference between the light
mount detected by the light amount detecting means and a light
amount target value becomes small, a junction temperature detecting
means for calculating junction temperature of the light emitting
element, and a setting means for setting the light amount target
value in accordance with the junction temperature detected by the
junction temperature detecting means, in which the light emitting
element has three color emitting elements including a red-light
emitting element generating light of a red wavelength component, a
green-light emitting element generating light of a green wavelength
component and a blue-light emitting element generating light of a
blue wavelength component, and in which the setting means sets the
light amount target value to be applied to each color emitting
element of the light emitting element by using three temperature
correction functions for each said color light emitting element
each pertaining to a function involving the respective color
emitting element and junction temperature variation of one of the
three color emitting elements such that for a first color emitting
element three respective temperature correction functions are
utilized which include a first temperature correction function
pertaining to a function involving the first color emitting element
and junction temperature variation of the first color emitting
element, a second temperature correction function pertaining to a
function involving the first color emitting element and junction
temperature variation of a second color emitting element, and a
third temperature correction function pertaining to a function
involving the first color emitting element and junction temperature
variation of a third color emitting element.
6. The display device according to claim 5, wherein the light
amount target value is set based on the difference between a first
junction temperature detected by the junction temperature detecting
means in a state that the light emitting element is driven in a
first drive condition and a second junction temperature detected by
the junction temperature detecting means in a state that the light
emitting element is driven in a second drive condition.
7. The display device according to claim 6, wherein the first drive
condition is the optimum drive condition of the light emitting
element which has been previously set.
8. The display device according to claim 5, wherein the junction
temperature detecting means includes a current reading means for
reading drive current supplied to the light emitting element, a
voltage reading means for reading drive voltage applied to the
light emitting element, a temperature measuring means for measuring
peripheral temperature of the light emitting element, a storage
means for storing thermal resistance between the light emitting
element and the temperature measuring means, and a computing means
for calculating junction temperature of the light emitting element
by using the drive current read by the current reading means, the
drive voltage read by the voltage reading means, the peripheral
temperature measured by the temperature measuring means and the
thermal resistance stored in the storage means.
9. An illumination device comprising: a light emitting element to
be a light source; a light amount detecting unit configured to
detect the amount of light emitted by the light emitting element; a
light emitting element drive unit configured to control drive
current supplied to the light emitting element so that the
difference between the light mount detected by the light amount
detecting unit and a light amount target value becomes small; a
junction temperature detecting unit configured to calculate
junction temperature of the light emitting element; and a setting
unit configured to set the light amount target value in accordance
with the junction temperature detected by the junction temperature
detecting unit, in which the light emitting element has three color
emitting elements including a red-light emitting element generating
light of a red wavelength component, a green-light emitting element
generating light of a green wavelength component and a blue-light
emitting element generating light of a blue wavelength component,
and in which the setting means sets the light amount target value
to be applied to each color emitting element of the light emitting
element by using three temperature correction functions for each
said color light emitting element each pertaining to a function
involving the respective color emitting element and junction
temperature variation of one of the three color emitting elements
such that for a first color emitting element three respective
temperature correction functions are utilized which include a first
temperature correction function pertaining to a function involving
the first color emitting element and junction temperature variation
of the first color emitting element, a second temperature
correction function pertaining to a function involving the first
color emitting element and junction temperature variation of a
second color emitting element, and a third temperature correction
function pertaining to a function involving the first color
emitting element and junction temperature variation of a third
color emitting element.
10. A display device comprising: an illumination device irradiating
light; a light modulation unit configured to modulate light
irradiated by the illumination device; and a projection unit
configured to project light modulated by the light modulation unit,
and wherein the illumination device includes a light emitting
element to be a light source, a light amount detecting unit
configured to detect the amount of light emitted by the light
emitting element, a light emitting element drive unit configured to
control drive current supplied to the light emitting element so
that the difference between the light mount detected by the light
amount detecting unit and a light amount target value becomes
small, a junction temperature detecting unit configured to
calculate junction temperature of the light emitting element, and a
setting unit configured to set the light amount target value in
accordance with the junction temperature detected by the junction
temperature detecting unit, in which the light emitting element has
three color emitting elements including a red-light emitting
element generating light of a red wavelength component, a
green-light emitting element generating light of a green wavelength
component and a blue-light emitting element generating light of a
blue wavelength component, and in which the setting unit sets the
light amount target value to be applied to each color emitting
element of the light emitting element by using three temperature
correction functions for each said color light emitting element
each pertaining to a function involving the respective color
emitting element and junction temperature variation of one of the
three color emitting elements such that for a first color emitting
element three respective temperature correction functions are
utilized which include a first temperature correction function
pertaining to a function involving the first color emitting element
and junction temperature variation of the first color emitting
element, a second temperature correction function pertaining to a
function involving the first color emitting element and junction
temperature variation of a second color emitting element, and a
third temperature correction function pertaining to a function
involving the first color emitting element and junction temperature
variation of a third color emitting element.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
The present application claims priority from Japanese Patent
Application No. JP 2008-032743, filed in the Japanese Patent Office
on Feb. 14, 2008, the entire content of which is incorporated
herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an illumination device and a display
device including the same.
2. Description of the Related Art
In recent years, an illumination device using a light-emitting
diode (hereinafter, "LED") as a light source is utilized in various
fields. For example, in projective-type display devices, there
exist a device including an illumination device having three types
of LEDs as a light source, which generate light of wavelengths
corresponding respective color components of red, green and blue
which are three primary colors of light. The display device of this
type adds lights generated by three types of LEDs to obtain white
light. At that time, the color balance of white light obtained by
combining three colors (hereinafter, "white balance") chiefly
depends on the relative relationship of light intensity of
respective colors. Usually, the white balance is adjusted at the
time of factory shipping or the like, however, in actual use after
that, there is a case that light-emitting characteristics of the
LEDs vary due to temperature change or secular change and the white
balance is lost.
For example, in the following JP-A-2004-184852 (Patent Document 1),
a technique in which the amount of light from LEDs as light sources
is detected by optical sensors (photosensors) to adjust the white
balance in accordance with the detected amount of light, or a
technique in which a wavelength detection function that detects
wavelength information of LED is given to the optical sensors are
described. In JP-A-2007-87816 (Patent Document 2), there is
disclosed a technique in which a junction temperature of the LED is
measured by a temperature sensor as a peripheral temperature to
adjust setting items (values concerning power feeding to the LED)
in accordance with data of the setting items which is previously
stored based on the measured peripheral temperature.
SUMMARY OF THE INVENTION
However, the optical sensor having the wavelength detection
function is generally expensive, and is not adequate for
miniaturization. The light-emitting wavelength of the LED varies
according to change of drive current supplied to the LED or
temperature change. Therefore, for example, in the case that the
light-emitting efficiency of the LED is changed due to secular
change, the color balance is lost due to change of the
light-emitting wavelength even when drive current is adjusted for
compensating the change (lowering) of the amount of light. Also, in
the case that the light-emitting luminance of the LED is changed by
a video signal and the like, the color balance is lost because the
light-emitting wavelength is changed due to change of the junction
temperature of the LED even when the peripheral temperature of the
LED is fixed.
Thus, it is desirable to provide a configuration which can
appropriately correct deviation in the color balance due to change
of the light-emitting wavelength of the light emitting element even
when the expensive optical sensor having the wavelength detection
function is not used.
A first illumination device according to an embodiment of the
invention includes a light emitting element to be a light source, a
light amount detecting means for detecting the amount of light
emitted by the light emitting element, a light emitting element
drive means for controlling drive current supplied to the light
emitting element so that the difference between the light mount
detected by the light amount detecting means and a light amount
target value becomes small, a junction temperature detecting means
for calculating junction temperature of the light emitting element,
and a setting means for setting the light amount target value in
accordance with the junction temperature detected by the junction
temperature detecting means.
A first display device according to an embodiment of the invention
includes an illumination device irradiating light, a light
modulation means for modulating light irradiated by the
illumination device, and a projection means for projecting light
modulated by the light modulation means, in which the illumination
device has a light emitting element to be a light source,
a light amount detecting means for detecting the amount of light
emitted by the light emitting element, a light emitting element
drive means for controlling drive current supplied to the light
emitting element so that the difference between the light mount
detected by the light amount detecting means and a light amount
target value becomes small, a junction temperature detecting means
for calculating junction temperature of the light emitting element,
and a setting means for setting the light amount target value in
accordance with the junction temperature detected by the junction
temperature detecting means.
In the first illumination device and the first display device
according to the embodiments of the invention, the light mount
target value to be applied to the light emitting element is set in
accordance with the junction temperature of the light emitting
element detected by the junction temperature detecting means as
well as drive current to the light emitting element is controlled
by the light emitting element drive means so that the light amount
of the light emitting element detected by the light amount
detecting means corresponds to the set light amount target
value.
In a second illumination device of an embodiment of the invention,
which is according to the first illumination device, the setting
means sets the light amount target value based on the difference
between a first junction temperature detected by the junction
temperature detecting means in a state that the light emitting
element is driven in a first drive condition and a second junction
temperature detected by the junction temperature detecting means in
a state that the light emitting element is driven in a second drive
condition.
In a second display device of an embodiment of the invention, which
is according to the first display device, the setting means sets
the light amount target value based on the difference between a
first junction temperature detected by the junction temperature
detecting means in a state that the light emitting element is
driven in a first drive condition and a second junction temperature
detected by the junction temperature detecting means in a state
that the light emitting element is driven in a second drive
condition.
In the second illumination device and the second display device
according to the embodiments of the invention, the light amount
target value is set based on the difference between junction
temperatures detected when the light emitting element is driven in
different drive conditions.
In a third illumination device of an embodiment of the invention,
which is according to the second illumination device, the first
drive condition is the optimum drive condition of the light
emitting element which has been previously set.
In a third display device of an embodiment of the invention, which
is according to the second display device, the first drive
condition is the optimum drive condition of the light emitting
element which has been previously set.
In the third illumination device and the third display device
according to the embodiments of the invention, the light amount
target value is set based on the difference between the junction
temperature in a state that the light emitting element is driven in
the optimum driven condition and the junction temperature in a
state that the light emitting element is driven in a drive
condition which is different from the optimum drive condition.
In a fourth illumination device of an embodiment of the invention,
which is according to the first illumination device, the light
emitting element has a red-light emitting element generating light
of a red wavelength component, a green-light emitting element
generating light of a green wavelength component and a blue-light
emitting element generating light of a blue wavelength
component.
In a fourth display device of an embodiment of the invention, in
which is according to the first display device, the light emitting
element has a red-light emitting element generating light of a red
wavelength component, a green-light emitting element generating
light of a green wavelength component and a blue-light emitting
element generating light of a blue wavelength component.
In the fourth illumination device and the fourth display device
according to the embodiments of the invention, the light amount
target value is set in accordance with the junction temperature of
the light emitting element by respective light emitting elements
having different light emitting colors.
In a fifth illumination device of an embodiment of invention, which
is according to the fourth illumination device, the setting means
sets the light amount target value to be applied to the light
emitting element by each light emitting element of one color by
using three temperature correction functions prepared for each
light emitting color.
In a fifth display device of an embodiment of invention, in which
is according to the fourth display device, the setting means sets
the light amount target value to be applied to the light emitting
element by each light emitting element of one color by using three
temperature correction functions prepared for each light emitting
color.
In the fifth illumination device and the fifth display device
according to the embodiments of the invention, the light amount
target values applied to light emitting elements of respective
colors are set by using three temperature correction functions
prepared for respective light emitting colors.
In a sixth illumination device of an embodiment of the invention,
in which is according to the first illumination device, the
junction temperature detecting means includes a current reading
means for reading drive current supplied to the light emitting
element, a voltage reading means for reading drive voltage applied
to the light emitting element, a temperature measuring means for
measuring peripheral temperature of the light emitting element, a
storage means for storing thermal resistance between the light
emitting element and the temperature measuring means, and a
computing means for calculating junction temperature of the light
emitting element by using the drive current read by the current
reading means, the drive voltage read by the voltage reading means,
the peripheral temperature measured by the temperature measuring
means and the thermal resistance stored in the storage means.
In a sixth display device of an embodiment of the invention, in
which is according to the first display device, the junction
temperature detecting means includes a current reading means for
reading drive current supplied to the light emitting element, a
voltage reading means for reading drive voltage applied to the
light emitting element, a temperature measuring means for measuring
peripheral temperature of the light emitting element, a storage
means for storing thermal resistance between the light emitting
element and the temperature measuring means, and a computing means
for calculating junction temperature of the light emitting element
by using the drive current read by the current reading means, the
drive voltage read by the voltage reading means, the peripheral
temperature measured by the temperature measuring means and the
thermal resistance stored in the storage means.
In the sixth illumination device and the sixth display device
according to the embodiments of the invention, the junction
temperature of the light emitting element is detected in the state
that the light emitting element is driven (lighted) by supplying
drive current from the light emitting element drive means.
In the first illumination device and the first display device
according to the embodiment of the invention, for example, even
when the junction temperature of the light emitting element is
changed according to change of peripheral temperature, light
emitting luminance and the like of the light emitting element,
drive current to the light emitting element is controlled so that
the light amount (light emitting amount) of the light emitting
element corresponds to the light amount target value set in
accordance with the junction temperature, therefore, the light
amount of the light emitting element can be appropriately
maintained.
In the second illumination device and the second display device
according to the embodiments of the invention, the light amount
target value is set (setting change when the light amount target
value has been already set) based on the difference between
junction temperatures detected when the light emitting element is
driven in different drive conditions, therefore, it is possible to
appropriately set (or change) the light amount target value in
accordance with the change of the junction temperature associated
with the difference of the drive condition.
In the third illumination device and the third display device
according to the embodiments of the invention, it is possible to
appropriately set the light amount target value (setting change
when the light amount target value has been already set) according
to changes of the junction temperature of the light emitting
element when the light emitting element is driven in the optimum
drive condition and when the light emitting element is drive in
other drive conditions.
In the forth illumination device and the fourth display device
according to the embodiments of the invention, it is possible to
appropriately maintain color balance of light obtained by adding
(combining) lights generated by the light emitting elements of
respective colors by setting the light amount target value in
accordance with junction temperatures of respective light emitting
elements. Therefore, even when a light emitting wavelength of the
light emitting element changes with change of, for example, the
peripheral temperature or the light emitting luminance of the light
emitting element, deviation (particularly, losing of white balance)
in the color balance caused by the change of the light emitting
wavelength of the light emitting element can be appropriately
corrected without an expensive optical sensor having a wavelength
detection function).
In the fifth illumination device and the fifth display device
according to the embodiments of the invention, it is possible to
appropriately set light amount values to be applied to respective
light emitting elements so that the color balance of light obtained
by adding (combining) lights generated by the light emitting
elements of respective colors is fixed.
In the sixth illumination device and the sixth display device
according to the embodiments of the invention, it is possible to
detect the junction temperature of the light emitting elements in
real time.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic diagram showing a configuration example of a
display device according to an embodiment of the invention;
FIG. 2 is a flowchart showing a procedure of adjustment processing
of color balance of the display device which is performed at the
time of factory shipping; and
FIG. 3 is a flowchart showing a procedure of control processing of
the display device which is performed at the time of normal
use.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, specific embodiments of the invention will be
explained in detail with reference to the drawings. Note that the
technical range of the invention is not limited to the embodiments
described below and includes forms to which various modifications
and improvement are added within a scope in which specific
advantages obtained by constituent features of the invention or
combination thereof can be derived.
FIG. 1 is a schematic diagram showing a configuration example of a
display device according to an embodiment of the invention. The
shown display device is a projection-type display device, including
a computing unit 1, a storage unit 2, a LED drive unit 3, LEDs 4,
optical sensors 5, temperature sensors 6, light modulation devices
7, a light combining device 8, and a projection lens 9. The LEDs 4,
the optical sensors 5, the temperature sensors 6 and the light
modulation devices 7 are separately provided with respect to
respective color components (light emitting colors) of red, green
and blue which are three primary colors of light.
That is to say, the LEDs 4 are provided separately as a LED 4a
corresponding to a red wavelength component, a LED 4b corresponding
to a green wavelength component and a LED 4c corresponding to a
blue wavelength component. The optical sensors 5 are provided
separately as an optical sensor 5a corresponding to a red
wavelength component, an optical sensor 5b corresponding to a green
wavelength component and an optical sensor 5c corresponding to a
blue wavelength component. Similarly, the temperature sensors 6 are
provided separately as a temperature sensor 6a corresponding to a
red wavelength component, a temperature sensor 6b corresponding to
a green wavelength component and a temperature sensor 6c
corresponding to a blue wavelength component, additionally, the
light modulation devices 7 are provided separately as a light
modulation device 7a corresponding to a red wavelength component, a
light modulation device 7b corresponding to a green wavelength
component and a light modulation component 7c corresponding to a
blue wavelength component.
The computing unit 1 outputs a control signal to the LED drive unit
3 so that the color balance including the white balance becomes
optimum by using light amount data obtained from respective optical
sensors 5a, 5b and 5c, temperature data obtained from respective
temperature sensors 6a, 6b and 6c, further, data in which
inter-terminal voltages and drive currents of respective LEDs 4a,
4b and 4c obtained from the LED drive unit 3 is A/D converted and
data stored in the storage unit 2.
The storage unit 2 is used for storing various data including data
necessary for adjusting the color balance by the computing unit
1.
The LED drive unit 3 allows respective LEDs 4a, 4b and 4c to emit
light (to be lit) by supplying drive currents to respective LEDs
4a, 4b and 4c as well as changes (increase and decrease) drive
currents supplied to respective LEDs 4a, 4b and 4c based on a
control signal given from the computing unit 1.
The LED 4 is a light emitting element to be a light source for the
illumination device according to an embodiment of the invention.
The light emitting element includes three-types of LEDs 4a, 4b and
4c having different light emitting colors. More specifically, the
LED 4a is a red-light emitting element generating light of a red
wavelength component, the LED 4b is a green-light emitting element
generating light of a green wavelength component and the LED 4c is
a blue-light emitting element generating light of a blue wavelength
component. Respective LEDs 4a, 4b and 4c may include one LED,
respectively, or plural LEDs may be formed as a one group. It is
also preferable that a semiconductor laser (LD) as a light source
of the illumination device.
The optical sensor 5 is a light amount detecting means for
detecting the amount of light (light intensity) emitted by the LED
4. More specifically, the optical sensor 5a is a light amount
detecting means for detecting the light amount of a red wavelength
component generated by the LED 4a, the optical sensor 5b is a light
amount detecting means for detecting the light amount of a green
wavelength component generated by the LED 4b and the optical sensor
5c is a light amount detecting means for detecting the light amount
of a blue wavelength component. The above optical sensor 5 is
formed by using, for example, a photo diode outputting current in
proportion to the received amount of light.
The temperature sensor 6 is a temperature measuring means for
measuring peripheral temperature of the LED 4. More specifically,
the temperature sensor 6a is a temperature measuring means for
measuring peripheral temperature of the LED 4a, the temperature
sensor 6b is a temperature measuring means for measuring peripheral
temperature of the LED 4b and the temperature sensor 6c is a
temperature measuring means for measuring peripheral temperature of
the LED 4c.
The peripheral temperature of the LED 4 is a temperature in the
vicinity of the LED 4, which is the temperature specifically
defined as follows. That is, generally, the LED 4 has a structure
in which a LED chip functions as the LED 4 is sealed in a hollow
package (sealing body) in an airtight state. Therefore, the LED 4
and the package sealing the LED 4 are in a state that they are
thermally connected. In such case, the peripheral temperature of
the LED 4 corresponds to the temperature of the package which seals
the LED chip. The package temperature may be, for example, the
temperature inside the package, the temperature of the package
itself or the temperature outside the package provided that it is
the position in the vicinity of the LED 4 as well as calculation of
heat conductivity is possible. Particularly, it is desirable that
the peripheral temperature of the LED 4 is the temperature of the
position near the LED 4 to be a heating source when calculating a
later-described junction temperature accurately. In general, the
LED 4 is used by being combined with a heat release body such as a
heat sink. In such case, assume that a mounting member (a member
having heat conductivity) is used for mounting the package of the
LED 4 on the heat release body, the temperature sensor 6 is
provided in the same surface as an attaching surface of the
mounting member to which the package of the LED4 is attached
(preferably, a position near the package of the LED4), and the
temperature measured by the temperature sensor 6 is dealt with as
the peripheral temperature of the LED4.
The light modulation device 7 is a light modulation means
modulating light on an optical path of light generated by the LED
4. More specifically, the light modulation device 7a is a light
modulation means allowing light of a red wavelength component
generated by the LED 4a to selectively transmit (or reflect), the
light modulation device 7b is a light modulation means allowing
light of a green wavelength component generated by the LED 4b to
selectively transmit (or reflect) and the light modulation device
7c is a light modulation means allowing light of a blue wavelength
component generated by the LED 4c to selectively transmit (or
reflect). The modulation of light by the modulation device 7 is
performed based on a video signal. In this case, assume that each
of light modulation devices 7a, 7b and 7c includes a transmissive
liquid crystal device (LCD) and a polarizing plate. However, the
invention is not limited to this, and for example, a reflective
liquid crystal device and the polarizing plate or a DMD (digital
mirror device) can be used as a light modulation device.
The light combining device 8 combines light of respective color
components which is incident from respective LEDs 4a, 4b and 4c
through the light modulation devices 7a, 7b and 7c corresponding to
respective LEDs. The light combining device 8 is formed by using,
for example, a light combining prism.
The projection lens 9 projects light (combined light of three
colors) radiated from the light combining device 8 on a screen
10.
In the display device including the above configuration, lights
emitted at the LEDs 4a, 4b and 4c are incident to light modulation
devices 7a, 7b and 7c corresponding to respective LEDs and lights
optically modulated so as to correspond to video signals according
to color components are combined at the light combining device 8.
Further, light combined at the light combining device 8 is
outputted to the projection lens 9 and video enlarged at the
projection lens 9 (still pictures, moving pictures and the like) is
projected on the screen 10. At that time, drive currents given to
respective LEDs 4a, 4b and 4c are adjusted by the LED drive unit 3
in accordance with a control signal outputted from the computing
unit 1.
Respective optical sensors 5a, 5b and 5c receive part of light
generated by the LED 4a, 4b and 4c corresponding to respective
optical sensors to generate currents in proportion to the amount of
received light. The computing unit 1, after converting current
outputted from respective optical sensors 5a, 5b and 5c into
voltages, reads data which has been A/D converted by a not-shown
A/D converter as light amount data. Accordingly, light amount data
detected by the optical sensor 5a is taken by the computing unit 1
as the light emitting amount of the LED 4a. Similarly, light amount
data detected by the optical sensor 5b is taken by the computing
unit 1 as light emitting amount of the LED 4b and light amount data
detected by the optical sensor 5c is taken by the computing unit 1
as the light emitting amount of the LED 4c.
Respective temperature sensors 6a, 6b and 6c convert temperatures
measured by the sensor themselves into electric signals and output
them. The computing unit 1 reads electric signals outputted from
respective temperature sensors 6a, 6b and 6c as temperature data of
peripheral temperatures of the LEDs 4a, 4b and 4c corresponding to
respective temperature sensors. Accordingly, temperature data
measured by the temperature sensor 6a is taken by the computing
unit 1 as the peripheral temperature of the LED 4a. Similarly,
temperature data measured by the temperature sensor 6b is taken by
the computing unit 1 as the peripheral temperature of the LED 4b,
and temperature data measured by the temperature sensor 6c is taken
by the computing unit 1 as the peripheral temperature of the LED
4c.
In such operation state, the color balance of white light projected
from the projection lens 9 on the screen 10, namely, the white
balance can be adjusted by changing drive currents supplied from
the LED drive unit 3 to respective LEDs 4a, 4b and 4c. Therefore,
the LED drive unit 3 performs a so-called white balance adjustment
in which drive currents to be supplied to respective LEDs 4a, 4b
and 4c are changed in accordance with a control signal outputted
from the computing unit 1 so that white light projected on the
screen 10 has desired chroma, usually when the display device is
shipped as a product. In order to perform the adjustment, a chroma
measure 11 for measuring chroma of video (a white picture)
projected on the screen 10 becomes necessary. The chroma data
measured by the chroma measure 11 is read by the computing unit 1.
Note that the chroma measure 11 is necessary for adjusting the
color balance, however, it is not necessary when the display device
is actually used. That is, the chroma measure 11 is a measure for
adjusting the color balance which is necessary at the time of
factory shipping (or at the time of readjustment after shipping)
and the like.
FIG. 2 is a flowchart showing a procedure of adjustment processing
of the color balance (white balance) of the display device
performed at the factory shipping. First, prescribed drive currents
(for example, drive currents set by default) are individually
supplied from the LED drive unit 3 to respective LEDs 4a, 4b and 4c
to light the respective LEDs 4a, 4b and 4c (Step S1). At this time,
the light modulation devices 7a, 7b and 7c performs modulation of
light so as to transmit incident light as it is in accordance with
a video signal for adjusting the color balance (video signal for
white display). Accordingly, lights emitted at respective LEDs 4a,
4b and 4c are combined at the light combining device 8 through the
light modulation devices 7a, 7b and 7c corresponding to respective
LEDs and the combined light is projected on the screen 10 by the
projection lens 9.
Next, the chroma of a picture (video) projected on the screen 10 is
measured by using the chroma measure 11 (Step S2). The chroma data
measured by the chroma measure 11 is taken by the computing unit
1.
Next, the computing unit 1 outputs a control signal designating the
adjustment amount of drive current to the LED drive unit 3 so that
the difference between chroma measured by the chroma measure 11 and
the reference chroma which is previously set (chroma supposed to be
optimum) becomes small, thereby adjusting (increasing or
decreasing) drive currents supplied from the LED drive unit 3 to
respective LEDs 4a, 4b and 4c (Step S3). The reference chroma is
chroma at which the white balance of video (same meaning as a
picture) displayed by projecting light on the screen 10 is optimum.
It is preferable that data of the reference chroma is stored in the
storage unit 2 in advance and read by the computing unit 1, or it
is also preferable that data is inputted in the computing unit 1 at
the time of adjustment.
Next, the computing unit 1 determines whether the chroma measured
by the chroma measure 11 corresponds to the reference chroma or not
(Step S4), and when it does not correspond, the process returns to
the above Step S2. When the measured chroma corresponds to the
reference chroma, the computing unit 1 reads drive currents
supplied from the LED drive unit 3 to respective LEDs 4a, 4b and 4c
and inter-terminal voltages of respective LEDs 4a, 4b and 4c in the
drive state at that time, namely, in a state in which respective
LEDs 4a, 4b and 4c are driven in the optimum drive condition
(condition in which color balance of three colors becomes optimum)
(Step S5). The "optimum drive condition of the LED" described here
means the drive condition of the LED in a state in which the color
balance is adjusted so that the chroma measured by the chroma
measure 11 corresponds to the reference chroma which is previously
set.
Next, the computing unit 1 reads peripheral temperatures of the
LEDs 4a, 4b and 4c measured by respective temperature sensors 6a,
6b and 6c (step S6). The temperatures read by the computing unit 1
are the peripheral temperatures of the LEDs 4 in a state in which
the adjustment of the color balance has been completed (that is,
the state in which the LEDs 4 are driven in the optimum drive
condition).
Next, the computing unit 1 calculates junction temperatures of
respective LEDs 4a, 4b and 4c by using data of drive currents,
inter-terminal voltages and peripheral temperatures of the LEDs
taken as the above in accordance with formulas (1) to (3) below
(Step S7). The junction temperature calculated here corresponds to
a "first junction temperature".
Tj0a=I0a.times.V0a.times.Tj-.theta.+T0a (1)
Tj0b=I0b.times.V0b.times.Tj-.theta.+T0b (2)
Tj0c=I0c.times.V0c.times.Tj-.theta.+T0c (3)
In the above formula (1), "Tj0a" is a junction temperature of the
LED 4a, "I0a" is a drive current of the LED 4a, "V0a" is an
inter-terminal voltage of the LED 4a, "Tj-.theta." is a thermal
resistance between the LED 4a and the temperature sensor 6a and
"T0a" is a peripheral temperature of the LED 4a measured by the
temperature sensor 6a. Similarly, in the above formula (2), "Tj0b"
is a junction temperature of the LED 4b, "I0b" is a drive current
of the LED 4b, "V0b" is an inter-terminal voltage of the LED 4b,
"Tj-.theta." is a thermal resistance between the LED 4b and the
temperature sensor 6b and "T0b" is a peripheral temperature of the
LED 4b measured by the temperature sensor 6b. Further, in the above
formula (3), "Tj0c" is a junction temperature of the LED 4c, "I0c"
is a drive current of the LED 4c, "V0c" is an inter-terminal
voltage of the LED 4c, "Tj-.theta.," is a thermal resistance
between the LED 4c and the temperature sensor 6c and "T0c" is a
peripheral temperature of the LED 4c measured by the temperature
sensor 6c.
The junction temperature of the LED is a temperature of a pn
junction of the LED which is a semiconductor light emitting device.
The inter-terminal voltage of the LED is drive voltage applied to
the LED, strictly, corresponding to anode-cathode voltage of the
LED. It is preferable that the inter-terminal voltage is applied by
being read from the storage unit 2 in which a value measured by
using a measure in advance in stored, or that it is measured in the
actual operation state. Since the inter-terminal voltage of the LED
does not change after it is set once, for example, it can be used
if necessary by reading from the storage unit 2 in which a measured
value measured at the time of factory shipping is stored.
Additionally, the individual difference of the inter-terminal
voltages of the LEDs 4 is extremely small, therefore, a fixed
voltage value previously determined by specifications of the LED 4
can be used for calculating the junction temperature as a "terminal
voltage" by storing the value in the storage unit 2 or
incorporating the value in a program for computing. When the
inter-terminal voltage is actually measured, voltage between
terminals to which two wirings used for supplying drive current by
the LED drive unit 3 to the LED 4 can be measured instead of the
anode-cathode voltage of the LED 4. The thermal resistance
"Tj-.theta." is calculated by simulation based on a material, a
shape and the like of the LED 4. The thermal resistance is stored
in the storage unit 2 and read by the computing unit 1 if
necessary. In the case that the setting condition in the LEDs 4 and
the temperature sensors 6 are common to all respective color
components of RGB, a common value will be applied concerning the
thermal resistance "Tj-.theta.". When the chip of the LED 4 having
the temperature sensor function is used, a value of the thermal
resistance provided by a manufacturer manufacturing the LED chip
can be used.
Next, the computing unit 1 reads light amount data S0a, S0b and S0c
from respective optical sensors 5a, 5b and 5c (Step S8). The light
amount data read by the computing unit 1 is the light amount of the
LED 4 in the state in which the adjustment of color balance has
been completed as described above. The light amount data S0a is
light amount data of the LED 4a read from the optical sensor 5a,
the light amount data S0b is the light amount data of the LED 4b
read from the optical sensor 5b and light amount data S0c is light
amount data of the LED 4c read by the optical sensor 5c.
Next, the computing unit 1 stores the junction temperatures Tj0a,
Tj0b and Tj0c calculated in the above Step S7 and the light mount
data S0a, S0b and S0c read in the above Step S8 in the storage unit
2, respectively (Step S9). That is the end of the adjustment
processing at the time of factory shipping. The electrical
connection between the computing unit 1 and the chroma measure 11
is cut off after the adjustment processing is completed.
FIG. 3 is a flowchart showing a procedure of control processing of
the display device performed at the time of normal use. The normal
use means a stage in which the display device is normally operated
to be used at least after the adjustment of the color balance has
been completed (usually, a stage in which the display device is
used in accordance with an operation manual by a user who purchased
the display device).
First, drive currents are supplied from the LED drive unit 3 to
respective LEDs 4a, 4b and 4c in accordance with the control signal
outputted from the computing unit 1, thereby, the computing unit 1
reads drive currents Ia, Ib and Ic supplied from the LED drive unit
3 to respective LEDs 4a, 4b, 4c and the inter-terminal voltages Va,
Vb, Vc of respective LEDs 4a, 4b, 4c (Step S11) in a state in which
respective LEDs 4a, 4b and 4c are lighted (on), namely, in the
state in which respective LEDs are driven in the normal drive
condition (second drive condition).
Next, the computing unit 1 reads the peripheral temperatures Ta, Tb
and Tc of the LEDs 4a, 4b and 4c measured by respective temperature
sensors 6a, 6b and 6c (Step S12).
Next, the computing unit 1 calculates junction temperatures Tja,
Tjb and Tjc of respective LEDs 4a, 4b and 4c (Step S13) based on
the following formulas (4) to (6) by using data of drive currents
Ia, Ib and Ic inter-terminal voltages Va, Vb and Vc read in the
above Step S11 as well as peripheral temperatures Ta, Tb and Tc
read in the above Step S12. The junction temperature calculated
here corresponds to the "second junction temperature".
Tja=Ia.times.Va.times.Tj-.theta.+Ta (4)
Tjb=Ib.times.Vb.times.Tj-.theta.+Tb (5)
Tjc=Ic.times.Vc.times.Tj-.theta.+Tc (6)
Next, the computing unit 1 reads junction temperatures Tj0a, Tj0b
and Tj0c of respective LED 4a, 4b and 4c stored in the storage unit
2 (Step S14).
Next, the computing unit 1 calculates differences .DELTA.Tja,
.DELTA.Tjb, and .DELTA.Tjc between the junction temperatures Tja,
Tjb and Tjc calculated in the actual use state and the junction
temperatures Tj0a, Tj0b and Tj0c read from the storage unit 2 by
each light emitting wavelength component (light emitting colors) of
the LED 4a, 4b and 4c in accordance with the following formulas (7)
to (9) (Step S15). .DELTA.Tja=Tja-Tj0a (7) .DELTA.Tjb=Tjb-Tj0b (8)
.DELTA.Tjc=Tjc-Tj0c (9)
Next, the computing unit 1 reads light amount data S0a, S0b and S0c
of respective optical sensors 5a, 5b and 5c stored in the stored
unit 2 (Step S16).
Next, the computing unit 1 calculates light amount target values
Sta, Stb and Stc of respective optical sensors 5a, 5b and 5c in
accordance with the following formulas (10) to (12) (Step S17) by
using temperature correction functions faa(.DELTA.t),
fab(.DELTA.t), fac(.DELTA.t), fba(.DELTA.t), fbb(.DELTA.t),
fbc(.DELTA.t), fca(.DELTA.t), fcb(.DELTA.t), and fcc(.DELTA.t) with
respect to respective light emitting colors, which have been
experimentally obtained from characteristics of respective LEDs 4a,
4b and 4c in advance. The light amount target value Sta is applied
to the LED 4a. The light target value Stb is applied to the LED 4b
and the light amount target value Stc is applied to the LED 4c.
Accordingly, the setting of the light amount target value is made
by each light emitting color.
Sta=S0a.times.(faa(.DELTA.Tja)+fab(.DELTA.Tjb)+fac(.DELTA.Tjc)+1)
(10)
Stb=S0b.times.(fba(.DELTA.Tja)+fbb(.DELTA.Tjb)+fbc(.DELTA.Tjc)+1)
(11)
Stc=S0c.times.(fca(.DELTA.Tja)+fcb(.DELTA.Tjb)+fcc(.DELTA.Tjc)+1)
(12)
In the above formulas (10) to (12), the temperature correction
function is a function of prescribing to what degree the light
amounts of respective LEDs 4a, 4b and 4c are corrected for keeping
the color balance to be fixed before and after change of the
junction temperature in the case that the junction temperature of a
certain LED 4 is changed by .DELTA.T. More specifically, the
temperature correction function faa (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4a with
respect to the junction temperature variation (.DELTA.Tja) of the
LED 4a generating light of the red wavelength component, the
temperature correction function fab (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4a with
respect to the junction temperature variation (.DELTA.Tjb) of the
LED 4b generating light of the green wavelength component and the
temperature correction function fac (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4a with
respect to the junction temperature variation (.DELTA.Tjc) of the
LED 4c generating light of the blue wavelength component.
The temperature correction function fba (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4b with
respect to the junction temperature variation (.DELTA.Tja) of the
LED4a generating light of the red wavelength component, the
temperature correction function fbb (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4b with
respect to the junction temperature variation (.DELTA.Tjb) of the
LED4b generating light of the green wavelength component, and the
temperature correction function fbc (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4b with
respect to the junction temperature variation (.DELTA.Tjc) of the
LED4c generating light of the blue wavelength component.
The temperature correction function fca (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4c with
respect to the junction temperature variation (.DELTA.Tja) of the
LED4a generating light of the red wavelength component, the
temperature correction function fcb (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4c with
respect to the junction temperature variation (.DELTA.Tjb) of the
LED4b generating light of the green wavelength component, and the
temperature correction function fcc (.DELTA.t) is a function of
prescribing the rate of light amount correction of the LED 4c with
respect to the junction temperature variation (.DELTA.Tjc) of the
LED4c generating light of the blue wavelength component.
The reason that the temperature correction function with respect to
each light emitting color of the LED 4 is used is that it is
desirable that not only the light amount of the LED 4 in which the
junction temperature has been changed but also light amounts of
respective LEDs 4a, 4b and 4c are corrected at the same time in
order to maintain the color balance to be fixed even when the
junction temperature of the LED 4 is changed, in the case that the
adjustment of the color balance including the white balance is
performed by increasing or decreasing light amounts of respective
LEDs 4a, 4b and 4c. Therefore, three temperature correction
functions are prepared for each LED of one color. However, the
invention is not limited to this, and it is preferable that one
temperature correction function is prepared for the LED of one
color so as to correct only the light amount of the LED 4 in which
the junction temperature has been changed. Assuming that all values
of the temperature correction functions are 0 (zero), the light
amount data S0a, S0b and S0c at the time of factory shipping, which
has been read from the storage unit 2 are set as the light amount
target values Sta, Stb and Stc as they are.
Next, the computing unit 1 reads the light amount data Sa, Sb and
Sc from respective optical sensors 5a, 5b and 5c (Step S18).
Next, the computing unit 1 adjusts (increases or decreases) drive
currents supplied from the LED drive unit 3 to respective LEDs 4a,
4b and 4c (Step S19) by outputting the control signal designating
adjustment amounts of drive currents to the LED drive unit 3 so
that differences between the light amount data Sa, Sb and Sc of
respective optical sensors 5a, 5b and 5c read in the above Step S18
and the light mount target values Sta, Stb and Stc set in the above
Step S17 become small (ideally, so as to be Sa=Sta, Sb=Stb and
Sc=Stc).
When the LED drive unit 3 adjusts drive currents to be supplied to
respective LEDs 4a, 4b and 4c based on the control signal from the
computing unit 1, in the case that the drive current is supplied to
the LED in a form of a pulse waveform, it is possible to adjust the
drive current by changing a peak current value (wave height value)
or the duty ratio of pulse waves. Particularly, it is preferable
that the duty ratio of pulse waves is changed for suppressing
change of the light emitting wavelength of the LED (change of
chroma) associated with the adjustment of drive current.
The display device is operated in accordance with the control
processing as described above, thereby maintaining the color
balance adjusted so as to be a desired chroma at the time of
factory shipping in that state even in a normal use. Therefore, it
is possible to appropriately correct deviation in the color balance
associated with change of the peripheral temperature of the LED,
luminance change of the LED, or secular change of characteristics
of the LED.
In the above embodiment, the case that the white balance is
adjusted as an example of the color balance has been explained,
however, the invention is not limited to this, and it can be
applied to cases that color balances other than white color are
adjusted.
Also in the above embodiment, the function of setting the light
mount target value in accordance with the junction temperature is
allowed to be possessed by all three types of LEDs 4a, 4b and 4c
having different light emitting colors, however, the invention is
not limited to this, and it is preferable that only one or two
types of LEDs are allowed to have the above setting function, and
that drive current is controlled by taking the light amount data
which is read in the adjustment at the time of factory shipping as
the light mount target value with respect to the LED which does not
have the setting function.
The illumination device according to an embodiment of the invention
is not limited to the one used for a projection-type display device
but, for example, the illumination device used for a display device
such as a direct-view type LCD which requires the illumination
device.
It should be understood by those skilled in the art that various
modifications, combinations, sub-combinations and alternations may
occur depending on design requirements and other factors insofar as
they are within the scope of the appended claims or the equivalents
thereof.
* * * * *